Re: RC: Re: Re:overweight an issue? - Weight vs. lean mass

["Susan Garlinghouse" <suendavid@worldnet.att.net>]

> RWR? Might help my slow thinking process if you avoid acronyms.

Rider weight ratio.  Sorry, didn't think it was a leap.



> Is that another word for "in a catabolic state"?

Same thing.  Burning lean muscle mass.


>
>  >and has burned up its own
>  lean muscle mass and glycogen stores---thus, less motor available and a
>  smaller fuel tank.  The horse runs out of glycogen and into metabolic
>  trouble, and now "mpg" *has* made a difference.>
>
> Don't get the "mpg" reference here. I am now deeply confused.

A horse with a small rider is going to burn fewer calories per miles to
cover the same number of miles.  The same horse with heavy rider is going to
burn more calories per mile.  Thus the smaller load is more efficient, in
that they're burning less fuel to go 100 miles.  But the assumption has been
that with a large load,  the horse doesn't have the onboard fuel capacity to
go just as far.  This study says they do, assuming the horse is in good body
condition.

Now let's say the same horse is excessivly thin--I called it cachexic, you
called it in a catabolic state.  Same thing---the horse hasn't been getting
enough calories and so to fuel the energy demand during conditioning, he's
been burning up his own lean muscle mass.  He might be aerobically fit as
hell, but the lean muscle isn't there to support it and actually drive the
horse forward.  The net effect is that he has the same muscle mass available
as a horse with considerably less conditioning---plus, less potential muscle
glycogen storage available (at least, hypothetically, none of this is
proven, but I'm working on it).  Now you put the heavyweight rider on this
thin, catabolic horse.  He's burning more calories per mile because of the
extra weight, but the critical factor is that now he has *less lean muscle
available and less glycogen onboard*---hence, he's relying more heavily on
anaerobic metabolism, reaches fatigue and glycogen depletion faster and is
going to be the first to get into metabolic trouble.  Under THOSE
circumstances, the size of the rider matters, because it directly affects
the calories required for each mile of trail.

Therefore, my hypotheses is that body fat is not an indication of
triglycerides available onboard for fatty acid oxidation---even a skeletal
horse still has sufficient body fats, 7-8% I think.  What I'm saying is that
condition score is an indicator of the catabolic or anabolic state of the
horse, and whether the horse had had sufficient substrates to sufficiently
build lean muscle mass and store liver and muscle glycogen.  Without taking
that into account, trying to draw conclusions about the effect of rider
weight is just barely skimming the surface of a very deep pond.


Susan G